1. Field of the Invention
This invention relates generally to radiographic imaging. More particularly, the invention relates to a radiographic image marking system for identifying and more clearly imaging certain protruding anatomical features in radiographic imaging applications where the anatomy of interest is at least partially compressed in making the image.
2. Description of Related Art
It has been recognized that there is often a need to mark certain anatomical structure in radiographic imaging applications for the convenience of medical personnel interpreting the images and to reduce the probability of uncertainty, confusion, or mistake concerning the nature of the anatomical structure. This is true for example in mammography, where the breast is compressed and certain features, particularly moles and the like for example, protrude from the surrounding skin of the patient. It is known that structure which protrudes from the surrounding epithelium, such as moles for example, can produce artifactal images which may be confused with internal structural abnormalities. In such applications an image susceptible to misinterpretation may result.
In the past such structure was identified and marked with radiopaque markers such as solder wire or lead shot taped to the skin, or later marker labels incorporating radiopaque markers made of coated lead or bismuth for example attached to an adhesive base for securing the marker temporarily to the skin of the patient. It has been recognized that it is desirable in addition to marking the location of the protruding structure to provide for more clear imaging of the structure itself. To this end a marker ring comprising a torroidal marker formed of a material partially opaque to imaging radiation, such as a rubber material for example, has been used. The ring marks the location of the structure of interest and also prevents the structure from being entirely compressed, for example in mammography applications in which the breast is compressed during the imaging process. This produces an image of the structure as well as the marker ring as disclosed and described for example in U.S. Pat. No. 5,383,233 issued to Donald G. Russell Jan. 17, 1995.
While the marking system disclosed in the Russell '233 patent allows improved imaging of the structure marked, certain limitations inherent in this system have been recognized. In order to prevent compression of the anatomical structure marked the marker must have a thickness associated with it. Variation of thickness of known markers of this type produces variation in the amount of material used and commensurately variation in the amount of radiation absorbed by the marker. Accordingly the image produced will show detail underneath the marker to a greater or lesser extent depending on the thickness of the marker. As can be appreciated anatomical structure that protrudes farther from the outer surface of the skin would require a thicker marker ring, and accordingly more radiation would be absorbed and the resulting image would show the structure underneath the marker more obscured. In practical application of the known system the protruding structure can be compressed to a more or less extent and markers of a rather more consistent thickness are employed.
What is recognized as needed, and has heretofore not been available, is a marking system which is consistent in producing an image of the protruding structure and the accompanying marker and mitigates the problems of compression of the protruding structure and provides the desired advantages mentioned. The present invention is directed to fulfilling this need.